As examples of a fluid pressure cylinder in which a plurality of pistons is coaxially incorporated in a cylinder main body, a thrust-force increasing type configured to apply a thrust force from a plurality of pistons to a piston rod, a multi-position type configured to selectively place a protruding end of a piston rod provided to a piston in a plurality of positions, a double-rod type configured to cause a piston rod provided to a piston to protrude from both ends of a cylinder main body, and the like are known.
A fluid pressure cylinder having a plurality of pistons, as just described, can be assembled by connecting, by bolts, a plurality of cylinder members each having a piston incorporated therein. However, in a case where bolts are used for connecting the cylinder members, it is necessary to provide, on the outside in a radial direction of a cylinder hole, attachment holes to which bolts are attached so as to extend in an axial direction, the cylinder main body is significantly increased in outer diameter in comparison with the cylinder hole, and the cylinder main body cannot be reduced in radial size. Therefore, it is not necessary to form attachment holes for bolts, by incorporating a plurality of pistons in a single cylinder main body, the cylinder main body can be reduced in radial size.
A fluid pressure cylinder in which a plurality of pistons is incorporated in a single cylinder main body is disclosed in, for example, Patent document 1 (Japanese Examined Utility Model Application Publication No. S48-14117), Patent document 2 (Japanese Utility Model Application Publication No. S52-24192), Patent document 3 (Japanese Unexamined Patent Application Publication No. H10-61609), and Patent document 4 (Japanese Unexamined Patent Application Publication No. S61-233208). Patent documents 1 and 2 each discloses a fluid pressure cylinder which has two pistons and in which the thrust force to be applied to piston rods is increased by applying fluid pressures to the pistons. Patent Document 3 discloses a fluid pressure cylinder which has three pistons and in which the thrust force to be applied to piston rods is increased by applying fluid pressures to the pistons. Patent Document 4 discloses a multi-position type fluid pressure cylinder in which pistons are provided in pressure chambers formed on respective sides of a partition wall, a first piston rod provided to one of the pistons so as to protrude from one end of the cylinder main body, and a second piston rod provided to the other of the pistons so as to interlock with the first piston rod.
In order to incorporate a plurality of pistons in a single cylinder main body, a plurality of pressure chambers are formed in the cylinder main body; therefore, a dividing wall, i.e., a partition wall for separating pressure chambers from each other are attached to the cylinder main body. In order to fix the partition wall to the cylinder main body, in the fluid pressure cylinder disclosed in Patent Document 2 or 4, the partition wall is fastened to the cylinder main body by screw members. In order to fasten the partition wall to the cylinder main body by the screw members in this manner, it is necessary to cause screw holes of the partition wall and the attachment holes of the cylinder main body to axially aligned with each other with the partition wall being inserted in the cylinder main body, and this cylinder encounters a problem that the attachment operation of the screw members cannot be easily carried out.
In the fluid pressure cylinder disclosed in Patent Document 3, a cylinder liner, i.e., a sleeve for positioning and fixing the partition wall is inserted in a cylinder main body. However, if the sleeve is used for positioning and fixing the partition wall, this cylinder encounters a problem that the number of parts is increased.
Furthermore, in the fluid pressure cylinder disclosed in Patent Document 1, a concave groove is formed on the outer peripheral surface of the partition wall, and a concave groove is formed on the inner peripheral surface of the cylinder main body so as to correspond to that of the partition wall. In an annular space formed by both concave grooves, a rod-like ring key is inserted from a through hole provided on the cylinder main body. However, in order to insert the rod-like ring key from the through hole provided on the cylinder main body, it is necessary to rotate the partition wall so as to correspond to the inserted ring key, it takes time to carry out this inserting operation, and it is difficult to form the concave groove on the inner peripheral surface of the cylinder main body.
It is therefore an object of the present invention to provide a fluid pressure cylinder improved in assembling performance so as to easily fix, to a cylinder main body, a partition wall for forming pressure chambers.